The present disclosure relates to a gas turbine structure. Moreover, the present disclosure relates to a gas turbine engine. Furthermore, the present disclosure relates to an aeroplane.
A gas turbine engine may be used as a jet engine. The term jet engine includes various types of engines, which admit air at relatively low velocity, heat it by combustion and shoot it out at a much higher velocity.
Accommodated within the term jet engine are, for example, turbojet engines and turbo-fan engines. The invention will below be described for a turbo-fan engine, but may of course also be used for other engine types.
A gas turbine structure, which may sometimes be denoted a case or frame, is used for supporting and carrying bearings, which in turn, rotatably support rotors. Conventional turbo fan engines have a fan frame, a mid-frame and an aft turbine frame. These frames constitute a gas turbine structure including a first housing, a second housing and a strut or a vane having a first end of the strut or vane being attached to the first housing and a second end being attached to the second housing. A vane or strut may be made of a composite material.
In order to achieve the attachment of the strut or vane to the first housing and second housing, respectively, U.S. Pat. No. 5,320,490 proposes the use of linking braces each one of which connecting a corner of the strut or vane to the first or second housing. However, the '490 solution does not necessarily provide an appropriate load distribution between the first and second housings via the strut or vane. Moreover, the '490 solution may result in large loads on bolts connecting the linking braces to the first housing or second housing.
It is desirable to provide a gas turbine structure which overcomes or ameliorates at least one of the disadvantages of the prior art, or to provide a useful alternative.
As such, the present disclosure relates to a gas turbine structure comprising a guide vane. The gas turbine structure further comprises a first housing and a second housing and the guide vane extends from the first housing to the second housing. Moreover, the guide vane comprises a leading edge and a trailing edge and the guide vane extends from the leading edge to the trailing edge along a mean camber line.
As used herein, the expression “mean camber line” is intended to mean the locus of points halfway between a suction side and a pressure side of the guide vane as measured perpendicular to the mean camber line itself.
The guide vane comprises a first attachment structure, a first fastening means, or a first fastener, and a second fastening means, or a second fastener. The first attachment structure comprises a stiffening member extending over at least a portion of a circumference of the first housing. Moreover, the stiffening member comprises a stiffening member centre point as measured along the mean camber line.
The first housing generally extends in a longitudinal direction which is parallel to a longitudinal axis as well as in a circumferential direction extending around the longitudinal axis. Moreover, the first housing generally has a first housing thickness in a radial direction. As used herein, the expression “stiffening member” refers to a member which provides stiffness in at least the radial direction. The stiffening member as discussed hereinabove preferably has a stiffening member width, i.e. an extension in a direction substantially parallel to the longitudinal direction, a stiffening member height, i.e. an extension in a direction substantially parallel to the radial direction, and a stiffening member length, i.e. an extension in a direction substantially parallel to the circumferential direction.
In order to provide an appropriate stiffness, at least in a direction parallel to the radial direction of the first housing, the stiffening member preferably has a stiffening member height which is at least 2 times, preferably at least 3 times, greater than the stiffening member width. Moreover, the stiffening member preferably has a stiffening member length which is at least 3 times, preferably at least 5 times, greater than the stiffening member width.
The first attachment structure is adapted to be releasably attached to the guide vane by the first and second fastening means such that the first fastening means is located at a first fastening position along the mean camber line and the second fastening means is located at a second fastening position along the mean camber line. Moreover, the attachment structure is attached to the first housing. The attachment structure may be releasably or fixedly attached to the first housing.
Generally, each one of the first fastening means and the second fastening means comprises an extension in a direction perpendicular to the mean camber line and the fastening means comprises a fastening means centre line in the direction perpendicular to the mean camber line. As used herein the expression “fastening position” relates to the position where the fastening means centre line, or an extension thereof, intersects the mean camber line.
According to the present disclosure, the first and second fastening positions are located on separate sides of the stiffening member centre point along the mean camber line.
During use, the guide vane may be subjected to loads such as drag loads from a fluid which is adapted to flow in the gas turbine structure and/or impact loads from ice particles or other types of particles which may enter the gas turbine structure during operation of the gas turbine of which the gas turbine structure forms a part. The above loads result in that attachment structures attaching the guide vane to the first housing and or second housing may be subjected to loads in the radial direction.
In order to transfer at least the radial load component imparted on the guide vane to the first housing in an appropriate manner, the attachment arrangement which attaches the guide vane to the first housing preferable has an appropriately high stiffness in at least the radial direction. It has been realized that a first attachment structure comprising a stiffening member according to the above may provide an appropriate stiffness in the radial direction. Moreover, the fact that the first and second fastening positions are located on separate sides of the stiffening member centre point along the mean camber line implies that an appropriate load distribution may be obtained from the guide vane to the first housing via the first attachment structure.
According to the present disclosure, the first fastening position, when measured along the mean camber line, may be located at a first distance from the stiffening member centre point and the second fastening position may be located at a second distance from the stiffening member centre point. The larger of the first and second distances may be less than 2 times, preferably less than 1.5 times, the smaller of the first and second distances.
According to the present disclosure, the attachment structure may be attached to a flange of the first housing.
According to the present disclosure, the first attachment structure may be adapted to be attached to the flange by means of at least a third fastening means. Moreover, the guide vane may extend in a guide vane direction from the first housing to the second housing and the third fastening means may extend in a third fastening direction which forms an angle with the guide vane direction.
According to the present disclosure, the first housing may extend in a longitudinal direction parallel to a longitudinal axis. Moreover, the first housing may extend in a circumferential direction around the longitudinal axis. The third fastening direction may be substantially parallel to the longitudinal direction.
According to the present disclosure, the first attachment structure may be fixedly attached to the first housing. Thus, the stiffening member may be fixedly attached to the first housing which in turn implies that the stiffening member may provide a large stiffness, at least in the radial direction.
A second aspect of the present invention relates to a gas turbine engine comprising a gas turbine structure according to the first aspect of the present invention.
A third aspect of the present invention relates to an aeroplane comprising a gas turbine engine according to the second aspect of the present invention.
Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.